following my post about the 08SUR-32S connectors, my ultimate goal is to monitor data exchanges

i beleive the info is likely to be usb data, i know it's pretty much master/slave approach

i think i'm likely to need what's often refered to as a "logic analyzer" (not sure though)

once i'd get the analog measures, i'll need to convert that into something usable

to acquire the data i was thinking of using maybe lxardoscopehttp://hackaday.com/2011/09/20/lxardoscope-is-a-linuxarduino-oscilloscope/but what will perform the sinusoide conversion into hexadecimal numeric data then ?

i've also though of the usbee combinaisonhttp://www.usbee.com/products.htmit looks like the cheapest option would beUSBee SX (hardware) ==> 169 USDUSBee Suite Pro (software, works on windows) ==> 299 USD

wow... even though both hardware/software may be good, honestly spending 500 USD sounds a bit extreme given the context. not to mention that i'm not even sure i'll be capable of using it anyway

i've also heard of the bus pirate thing http://dangerousprototypes.com/bus-pirate-manual/ => its 30 USD price tag sounds much more reasonable for educational purposes but still i'll have the analog data -> numeric data conversion to be performed somehow and i dont know how...?

anyone would help me point in the right direction ? i'm feeling kinda lost here :-|

That is nothing for a quality instrument, it won't even get you a decent scope. I spent £10,000 on a logic analiser (at work) when I lived in a house that cost me £8,000.

at work -- it used to be a factory assembling & repairing electronic devices -- they have a complete room full of dozens of unused supposedly expensive HP oscilloscopes somewhere in the back of a warehouse. They have not been used for years. kinda forgotten there. I asked if i could be donated one to have fun at home but i have been told that even though they are not used now, they are too expensive to be donated to employees. i have not been given a price, but it seems they were paid about several thousands EUR

i have used oscilloscopes back at school, it was kind of fun, but well... playing video games was fun too back then so i have not used any since high-school and embedded hardware is a recent hobby of mine. basically i am not sure i could do anything with an oscilloscope, and an expensive one feels like it might not be a good option of a n00b like me. not to mention that i doubt the oscilloscope would convert the UP/DOWN signals into usable bytes like wireshark does with network.

i have the feeling they will be sent to the trash in the next few monthsShould i take one in the trash for a future use then ?

That's the Saleae Logic, I've got one and they are great, no analog though.

Correct, but the original question was for a logic analyzer to monitor USB data exchanges so the Saleae logic would be his cheapest option.

as long as it gets the job done quickly without days of scratching my head not understanding what is going on==> i guess that's enough.

once i'm used to logic analysis then i will know what i need / want / dont want ==> then i may target something more professional.

for now "cheap that works" is exactly what i am looking for.

so will Saleae be able to understand/capture/decode raw usb frames ? (it is digital signal indeed, sorry if i wasn't clear on that)

Important: i have never read the hundreds pages long of official low level USB norm/protocol definition (what i will call here the "transport protocol"). However i am expert with the targeted peripheral "application-level protocol" i want to see on the device under test while it is operating.

a) whats the sample rate of the logic analyzer?b) whats the raw bit-speed of the usb link?

a) should be at least 10x of b)

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ok. i'll try to grab my hands on such oscillospes then (rumour is : "everyone wants one", so you guys are probably right anyway )

here is some info i found in the documentation regarding the usb device

Quote

USB Low Layer Protocol The integrated USB driver of the xxxxxxxxxxx device emulates a RS232 serial port.The xxxxxxxxxxx device is processed as a Communication Device Class (CDC), in accordance with the "USB Device Class Specifications, version 2.0" available from the http://www.usb.org/ web site, in "developers, document" section.The xxxxxxxxxxx device use the full speed transfer rate 12 Mbits/s, and is compatible with USB 1.1 and USB 2.0 Host Systems or hubs.

thanks madworm for the rule of thumb, it makes the picture much clearer now.

so if the transfer is 12Mbits/s i need about 120 "capture per second"assuming this is the Msps unit mentioned therewww.usbee.com/products.htm

then i need the USBee RX as it's the only one offering 100 Msps sampling rate. that's a 1945 USD

however, it seems the Beagle 12 made by totalphase http://www.totalphase.com/products/beagle_usb12/ would do the job for 475 USD

i have also seen the

Quote

You can get a Saleae Logic clone for $50, I'm talking about the Mini Logic on iTead Studio

on the other postis it this ? ==> http://iteadstudio.com/produce/seleae-logic-usbee-ax-usb-blaster/sorry if i sound stupid, but this is some sort of a "3 in 1" cheap chinese copy, right ? (no offense to chinese ppl)and it seems the highest sample rate is 24 msps which not enough, so buying this would just be a waste of money

so the Beagle 12 is the best option here then, right ? anyone ever tried it ?

It's surprising just how just how easy it is to make a logic analyzer. All you need is a FPGA board.

Making a scope is much harder, since you'll need to make a good analog front end. I recently finished a design for a digital power meter AFE and it was surprisingly hard to design even though it only has a 5kHz bandwidth. (The main problems were accuracy and crosstalk.)